The universal caster is disposed at a leg of a traveling body, such as a hand truck, a shopping cart, or a movable chair, thereby facilitating advancing and retracting of the traveling body, and in addition, freely turns in response to a change in orientation of the traveling body, thereby providing a function to allow a smooth traveling with the orientation of the traveling body being changed. Generally, the universal caster is comprised of a fixing plate that is fixed to the bottom face of a hand truck, or the like, a universal metal fitting that is disposed on the fixing plate through a bearing device, and a wheel that is pivotally supported by the universal metal fitting.
For a general traveling body, such as the hand truck, the shopping cart, or the movable chair, the above-mentioned conventional universal caster will cause no problem in particular. However, for example, in the case of a hand truck for loading and transporting a heavy substance, like a hand truck for use in a vehicle assembling plant, an iron wok, and the like, a significantly large weight load is imposed on each universal caster for the hand truck, and thus a large force is required especially at the time of initial operation or at the time of traveling over a step. In addition, since the load that is imposed on each universal caster is not always uniform, a partial distortion tends to be produced in the universal caster, thereby generating a possible obstacle for free turning of the universal caster.
As described above, conventionally, with a hand truck, and the like, for loading and transporting a heavy substance, a significantly large weight load has been imposed on each universal caster, thereby not only a large force having been required at the time of initial operation or at the time of traveling over a step, but also a partial distortion having tended to be produced in the universal caster, thereby having generated a possible obstacle for free turning of the universal caster. Embodiments of the present invention have been made to solve such a problem, and is intended to provide a universal caster that, with a hand truck, and the like, for loading and transporting a heavy substance, decreases the load at the time of initial operation or at the time of traveling over a step, allowing traveling without effort, and eliminating the possibility that an obstacle for free turning of the universal caster may be generated.